ABSTRACT: Antitrust is back in vogue at the U.S. Supreme Court. Whereas the Rehnquist Court decided few antitrust cases in its latter years (only one from 1993 to 1995, one each year from 1996 through 1999, and none from 2000 to 2003), the Roberts Court issued seven antitrust decisions in its first two years alone. Numerous commentators have characterized the Roberts Court’s antitrust decisions as radical departures that betray a pro-business, anti-consumer bias. While some of the decisions do represent significant changes from past practice (see, e.g., Leegin, which overruled the 1911 Dr. Miles rule of per se illegality for minimum resale price maintenance, and Twombly, which abrogated the infamous “no set of facts” pleading standard set forth in the 1957 Conley v. Gibson decision), the “pro-business/anti-consumer” characterization of the Roberts Court’s antitrust decisions is inaccurate. The characterization—caricature, really—fails to appreciate the fundamental limits of antitrust, a body of law that requires judges and juries to make fine distinctions between procompetitive and anticompetitive behaviors that frequently resemble each other. While false acquittals of anticompetitive conduct may harm consumers, so may false convictions of procompetitive actions. And efforts to eliminate errors in liability judgments are themselves costly. Optimal antitrust rules will therefore aim to minimize the sum of decision costs (the costs of reaching a liability decision) and expected error costs (the social losses from false convictions and false acquittals). Each of the Roberts Court’s antitrust decisions can be defended in light of this “decision-theoretic” approach, an approach calculated to maximize the effectiveness of the antitrust enterprise, to the ultimate benefit of consumers. This Article first describes the fundamental limits of antitrust and the decision-theoretic approach such limits inspire. It then analyzes the Roberts Court’s antitrust decisions, explaining how each coheres with the decision-theoretic model. Finally, it predicts how the Court will address three issues likely to come before it in the future: tying, loyalty rebates, and bundled discounts.